WEIGHT OF A FALLING DROP AND THE LAWS OF TATE.
VII.
1041
from the liquid. The solid phase between 60' and 95 ' was found to contain 58.93 per cent. of lead nitrate. The compound Pb(NO3),.3C,H,N contains 58.98 per cent. lead nitrate. This is the compound discovered and described by Schmujlow in 1897. Above 95' a compound was found which contained 86.2 per cent. of lead nitrate. Thisis evidently 3Pb(NO,),.2C,H5N, which contains 86.27 per cent. of lead nitrate. The transition points may be obtained from the curve, At 5 I O there is a transition point between Pb(N0,),.4C,H5N and Pb(N0,),.3C6H,N. A t 96' there is a transition point between Pb(NO3),.3C,H,N and 3Pb (NO,),. 2 C,H,N.
Summary. I n the foregoing investigation the solubility curve of lead nitrate and pyridine has been established between -19.4 and 110'. The results show that for this range of temperature there are three distinct crystalline compounds of lead nitrate and pyridine in equilibrium with the solution. The three compounds are: Pb(N0,),.4CjH5N; Pb(N0,),.3C5H5N; and 3Pb(NO3),.2C5H,N. Of these Pb(N0,),.4C,H5N and 3Pb(NO,),.2C,H,N have hitherto been unknown. UNIVERSITY O F WISCONSIN, MADISON,WIS.
[CONTRIBUTIONS FROM THE
HAVEMEYER LABORATORIES No. 192.1
OF COLUMBIA UNIVERSITY.
THE WEIGHT O F A FALLING DROP AND THE LAWS O F TATE VII. THE DROP WEIGHTS O F SOME OF THE LOWER ESTERS, AND THE SURFACE TENSIONS AND MOLECULAR WEIGHTS CALCULATED FROM THEM. BY J.
LIVINGSTON R.
MORGAN AND FREDEXICIK W.
SCHWAXTZ.
Received April 19,1911.
The object of this research was the further testing of the Morgan drop weight apparatus, for the purpose of ( I ) applying to additional substances the new definition of normal molecular weight in the liquid state; and ( 2 ) the direct comparison of the values of surface tension, as found from drop weight, with those from the capillary rise. The main difficulty encountered thus far in the comparison of drop weight results with those from capilliary rise has been the fact that no one agreeing value in many cases could be found from the work of the various observers of capillary rise, their results varying widely. I n order that any such variation might be avoided in the capillary rise results used in this research, those liquids, the lower esters, were selected, eight of which have been carefully studied by Ramsay and Aston,' each from observations a t three temZ. physik. Chew., 15, 98 (1894).
I042
GC3nCR 11
PHI'qIC 11, \TI) I&OOKGANIC.
peratures, in two capillary ttibes of differing bore. One great advantage of this form of coiiiparison is that it enables us a t the same time to ascertain the degree of accuracy in agreement that may be expected from the capillary rise method uiider ideal conditions, 1 e., where all is identical evcept the bore of the capillary used, and that it furnishes us with a criterion a'> to what I arLition in capillary rise results may be expected when nothing is identical in the work except the name of the liquid used - h o t h e r difficulty pre', iously encountered is also done away with in the use of these uniform results, ZIZ.,that due to the employment, in the calculation of a difierent density or rather difference in density as liquid and as vapor, a t the same temperature, for the same liquid, for the ialue of 7 = '1, hr. (d,-d,) is very decidedly dependent upon that. The tip used here was one with a straight, sharp, edge, slightly larger than that used by Xorgan and Thomssen, and smaller than that of Morgan and Daghlian, and was very approximately j 65 millimeters in diameter. Owing to the fact that a number of different weighing vessels were used on this apparatus, the total weights of vessel and drops are different in many cases for the same liquid a t different temperatures. I t is to be remembered here that in the use of this apparatus no comparison can be made between the weights of the j-drop blanks, except when they refer to the same liquid a t the same temperature. This is due to the fact that the blank is always held on the apparatus, with a drop hanging, for the same length of time that the zs-drop determinations of that liquid a t that temperature are allowed to stand and consequently i t always represents the weight of j drops, less the loss by evaporation. Two identical weights, then, for the T esse1 plus j drops, for different liquids, a t different temperatures, do not necessitate that the weight of I drop be the same in both cases; for that which has the greater drop weight, by its loss from e\ aporation, due to longer standing or higher vapor pressuie, will appear decidedly reduced in total weight It is only when the blanks are considered in connection with the determinations to which they refer that comparable results, L . e . , the w i g h t of I drop, are obtained.' I n Table I are giien the experimental results for benzene a t two temperatures, together with the values of w from the relationship w
(y ) '
=
(3: -
hB (288 5-t--6).
and that of k, calculated This is for the purpose
of standardizing the tip, the value of b , found being then used throughout for the calculation of the t, of the other liquids, and to prove from its constancy, a t \ ariom ternpcrdtuie5 of obseri ation, in any one 1 This IS complicated I u t h e r here h v the l a i t that it cork stupper \\AS used in tiic vLighing vessel in all thc cases giTen ~ 1 1 t a h neight lcss than io grams, and the cork, although constant in \\eight for each detelrnlnatlon, \$as not thc same throughout
WEIGHT OF -4 FALLING
DROP AND THE LAWS OF
1043
TATE. VII.
case, that the molecular weight of that liquid is normal, i. e., is the same as a liquid as i t is as a gas. In Table I1 are given the experimental, as well as the derived values for pyridine, which will serve as a preliminary test of the accuracy of the constant of standardization, k,, of the tip. As will be observed, this value of k, leads to a value of t, = 346.85 O, in place of 346.6', as calculated by Morgan from the results of Morgan and Higgins. From this result we may regard the value of k, as satisfactory. TABLEI.-BENZENE;M Wt. vessel 2j drops.
+
t. IO0
7.6515 7.6516 7.6515 7.6514
=
I O . 4610 10.4612 10.4611 10.4611
11.0194
drop.
7.0063
32.260
10.4611
27.915
W.
0.88956 0.85683
IO0
40.7
I
Mg.
w(;)*.
d.
1.
Wt. Av.
7.0063 7.0062 7.0064 7 .0063
7.6515
11.0194 11.0194 11.0193
288.5'.
=
+
Av.
11.0195
40.7
78; t,
Wt. vessel 5 drops.
32.260 27.915
636.72 564.90
2.3374 2 -3379
Av. kB
=
2.3373
TABLEII.-PYRIDINE;M = 79; t, =346.6'.' Wt. vessel 25 drops.
+
t.
8.5643 8.5642 8.5643 8.5644
00
Wt. vessel 5 drops.
+
AI.
7.6986 7 ' 6984 7.6984 7.6985
8'5643
I I . 7086
34.25
10.9472 10.9474 10,9475 10.9472 10.9472
I I . 7084 I I . 7085
I I . 7086
I I . 7087
11.7088 d.
1.
0. I O
34.25
.0014 0.9672 I
Av.
7.69847
10.9473
wt. t
drop,
w.
43.292
38.065
W.
43.292 38.065
796.31 716.58
346.8' 346.9O
In Tables I11 to XI11 are given the experimental values of the new liquids studied, viz., methyl formate, ethyl formate, propyl formate, See No. I V of this series.
1044
GENGR.II,,
IWYSIC.\I,
. I K D INORG~ISIC.
amyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl isobutyrate, and methyl butyrate. These, with the exception of the amyl formate, which was obtained froiii I h e r & Amend, and though purified before the determination, cannot be considered as satisfactory, were prepared especially for tlie work by the Hoffman C9r KropR' Chemical Company, and used as received. It will he noted here that the niasiniuin variation from the mean, .i. c . , where the "2j" determinations differ by 0 . 4 nig. and the blanks also differ by 0 . 0 3 ~amounts to only about o , o j per cent., the average \aria-. tion tieing n1ucli less. This, naturally, is simply tlie variable error, the abseiice of a constant error in any one case being slioivli better perhaps by the results given later:
'r h B LE I I I.-?VI ET11TL 15 1.
IO0
33.87
W t . vessel 25 drops.
9.8776 (1 .87j j 9.8773 9.8776
AV.
0.8775
9.8083 0 . 8083
9.80845
9.8087
9,7385 9.7356 9.7387 9.7387
9.73862
IO0
33.89
6.7887 6.7888 6.7888 6.7887
59.15
A!..
10.7920
10.7919
9.34512
-6.619
9.3337 9.3335 9.3338 9.3338
9'333G6
23.740
9.3260 9.3261
9 .32594
20.634
Wt. vessel 5 drops.
Av
.
Wt. I drop,
Mg*
6.2480 6.7887j
6.2480
6.2470
27.043
9.33557
24. I j
6.2478 6.2478 9.8186
10.7920 IO. 7921
9'345' 9 ' 3450 9.3451 9.3452
I drop. Mg.
I v - - ~ ~ I ~ k l Y l'lL ISOBUTYRATE; 32 = 102 0 8 ; t, obs.
=
267 6 ' .
2.3373
d.
f.
10.0' 33.9 60.1
fc
hl gs ,
*>.90033 0.87328 0,84295
623.57 567.55 505.06
26.619 23.740 20.634
Dyiies.
24.158 21.545
24.040 21.440 18.634
282.8 282.7 282.2
Ramsay and Aston; k B
2.3373
Dynes.
18.726
'
= 2 . 1 2 12.
---. = 0.01jo8
= o.oio46 cm.
cm.
. 7
tc
i.
563.6 487.3 4'5 . o
I0.O0
46.2 78.2
Renard and Guye; KB
;(y
t.
10.5' 30.5 41 .o
563 5 I9 496
563 .o 486. I 415 ' I
281.7 281,9 279.8 =
281.4 281.4 279.9
2.1108.
r(:)i.
IC
t.
283.2 282.4 282.0
5 5 .o 75.0
467
86.6
396
tc
282.2 280.9 280. 2
422
Surjace Tensiouj . ;R&A
i.
____A
-_--
24. 11 20.29 16.70
I0.O0 46.2 78.2
;hl&S
24.08
24.16
20.04 16.64
20.22
16.78* 2 1108 131 Sr S irom I,__ 2 3373
24.06
24.03 21.81
21.82 20.63 19.18
20.68
19. I8 17.04* 15.80*
17.02
15.78
TABLE XV.-ETHYL PROPIONATE; M =
102.08;
t, obs. = 2 7 2 .go.
1
10.0~
33.9 59.2
0.90106 0.87435 0,84502
27.043 24,152 21.194
633.16 576.93 517.92
2 1212
-
3 3373'
iR&G.
10.5' 30.5 41 . o 55 .o 75.0 86.6
from w
286.9
286.7 286.8
24.543 21.919 19.234
WEIGHT OF A FALLING DROP A S D THE LAWS OF TATE. VII.
1051
Table XV (Continued). Ramsay and Aston; k = 2 . 1 2 1 2 . T = 0.01708 cm. 7 = o 01046 cm.
----(y.
__A----
r(;)$. 1.
tC.
574.0 496.1 428.1
1o.oo
46.2 78.2
fc.
576.2 496.9 427.8
286.6 286. I 286.0
287.6 286.5 285.9
Surface Tensions. r R & A.
,------
1.
1o.oo 46.2 78.2
24.57 20.58 17.24
24,67
24.54
20.62
20.60
17.22
17.209
TABLE XVI.-METHYLPROPIONATE; M = 88.06; tc obs. d.
t.
0,92678 0.89758 0.86692
10.0'
34.7 59.8
-(:)". 582.31
W.
27.944 24.687 21.499
= 2 . 1 2 12
2 5 .360°
22.405 19.511
cm. r = 0.01046cm..
@T-263.
t.
46.2 78.2
I
1
tc .
T(;)$.
tc,
524.3 447 3 378.8
~57.4~.
265. I 265.4 266. I
7
I0.O0
=
(=22).
fC,
525. I4 468.04
Ramsay and Aston; kg 7 = 0.01708 cm.
2.1212 2.3373
from W - - - .
rM & S
530.2 450.2 381.9
2
263.1 262.8
266.0 264.4 264.2
Surface Tensions.
-
rR & A. t. 1O.O0
7 -
25.23 20.85 17.11
46.2 78.2
r M & S from
25.51 20.98 17.26
2.1212 2.3373
W-.
25.36 21.08
I7.30*
TABLE XVI1.-ETHYL FORMATE; M = 74 . o s ; tc = 235.2 O. t.
d.
0 . 1 ~
6.0 10.0 17.0 34.0
0.94697 0.93958 0.93458 0.92618 0.90418
W.
27.989 27.170 26.638 25.680 23.388
-(;)". 511.82
Ramsay and Aston; k~ cm.
=
2.1212. 7 = 0.01046 cm.
. ---
_ c _
1.
I0.O0 46.5 78.5
,(?$
25.401 24.658 24. I75 23.306 21.226
225. I 225.7 226.3 226.9 228.7
499'44 491.41 476.59 441.07
7 = 0.01843
.(=%).
tC
tc . tC.
443.5 371.5 309.2
225.I 227.6 230.3
446.0 375.5 309.1
226.3 229.5 230.3
GE"'EK.ZL,
0.95900 0.94651 0.91491
0.1'
10.0
34.2
PFIE'SIC.41, .\ND IXORGrZNIC.
29.307
531.23 508.54 452. IC)
27.801 24.160
26,592 2j.231
233.2
233.6 233 ' 7
Ramsay and Aston; k.13
21
,926
= 2.1212.
T = 0.01843 cm.
I
.z
0.01046
cm.
1. I0.O0
462.8
234.2
46.2 78.3
383.9 318.2
233.2
459.9 387.2 319.5
23,'. 2
2-32
.s
234.7 234.9
Siuface Teiisioizs. 2 1212 i M & S from w 2 3373'
rRBA. 1.
___A____
10.OO
25.22
46.2 78.3
20.32
25.23 20.29* 15.89 (Extrapolated through 44. I ")
25.06 20.49 16.35
16.28
TABI,~: XIX.--PROPULACLVATE; M f.
d.
0.I0
0.yIOoO
0.87229 0.84345
34.6 60,I
28.433 24.148 2I
,208
= 102
.os; tc obs.
661.20
289 . 0
577 .63 518.81
287.7 288. r
Rainsay and Aston; r 0.01708 cm.
25.804 21.9'5 19. "$7
, - 0,01046crn.
I
+,),( t
10.00
'
= 2 . 1 2 1-7
2
46.2 78.2
= 2 76. 2
24.80 20.86
24.88 20.84
'7.35
17.33
fc.
'4. j' 20.77 'j.?7*
WEIGHT OF A FALLING DROP .IND THE LAWS OF TATE. VII.
TABLE XX.-METHYL BCTYRATE;M = d.
f.
0.90925 0.88175 0.85375
10.0'
34.8 59.9
102.08; tc
649.76 591.82 533.07
21.964
294.0 294.0 294.0 =
281.3~.
595.0 514.5 446.9
22.610
19.930
r = 0.01046 cm.
r(:)'.
fc.
f.
25.340
2.1212.
= 0 01843 Em.
46.2 78.2
=
W
27.920 24.9'5
Ramsay and Aston; k B
I0.O0
obs.
10j3
tc.
591.7
296.5 294.8 294.9
511.8
444.4
295.0 293.5 293.7
Surface Tensions.
--
2.1212
r M & S from zv--
rR&A. 1.
2.3373
25.63 21.50
10.2O
46.2 78.2
25.34 21.40 17.98*
18.15
TABLE XXL-PROPYLFORMATE; M = 88.06;t, obs. 264.9'.
0.92850 0.92251 0.91726 o.gogOg 0.88873 0.85837
0.1'
5.4 10.0
17.0 34.8 60.3
28.604 27.941 27.337 26.458 24.298 21.419
594'88
25.960 25.358 24.809
260.6 261.I 261.2 261.7 263.9 267. I
583.60
573.16 558 .os
520.29 469' 39
Ramsay and Aston; k B r = 0.01843 cm.
24.012
22.05I '9.439
= 2.1212.
r = 0.01046 cm.
y_I
-
t. I0.O0
523.6
46.5 78.3
446.3 387 .o
524.4 447 ' I 385.2
262.8 262.9 266.8
263.2 263.3 265.9
Surface Tensiotis. f.
--
1o.oo 46.5
25.02 20.67
78.3
17.52
r R & A. -----
-25.06 20.71 7 7 -44
T M & S from
2 1212
w .
2 3373
24.81
20.83 17.61*
GENERAL, PHYSICAL AND INORGANIC.
TABLE XXII.--METHYLFORMATE; M = 60.03; t c obs. 2 1 4 ~ . d.
1.
0.
IO
6.7 10.0
16.4 2 7 .8
I .00300
29.893
0.99354 0.98892 0,97943 3.96320
28.860
[):
28.243 27.360 25.614 Ramsay
457.39 444.38 436.23 425.32 402.64 and Shields; ks
204.4 206. I = 2.1012.
?(f)"
383.9 363.7 343.2
30
202.6
4.
t,
ZC.
40
26.873 35.945 25.390 24,596 23.027
201.8 202.8
z,
x. 20°
2.1012 2.3373
ic
W
208.7
322.6 302.5 282.7
jOo
60 ' 70'
209. I
209.3
209. -7 2ro.o 210.5
Surface 'Temioizs. 7R &
t.
5.
7M
24.64 23.09 21.56
20O
30 40 50
18. 58 17.15
70
2.1012 2.3373'
24.11 22.72" 21.34" '9.95" 18.57" 17.19" (Extrapolated through 43.2 ")
20.05
60
s S from w-
TABLE X X I I I . - A 4 ~ r FORMATE; ~~ &I = 116.I : tc obs. t 10.0~
35.0 60.1
0.8882 0.8682 0.8420
27.464 24.693 21.904
706.26 645 * 73 584.62
Hornfray and Guye;
318.6 317.3 316.2
=
z0d.6~. 24.686 22.199 19.691
kB = 2 . 1 0 1 2 . ~
1.
569.5 497.8 432.2 Surface Tewsiows.
43.8O 77.8 10g.2
I
rH & G .
43.R0 77.8 109.2
21.64 18.40 15.52
TABLE XXIV.-ETmL t.
d.
W
2.1012 2.3373'
7hf Sr S from w21.51
18.12" I j .05* (Extrapolated through 49. I ")
ACETATE;41 = 88.06;tr obs.
$)! 582.86
W(
(
= 250. I
r =w-
'. ;.;;;;)Z
.
ti
0.1' 0.92421 27.940 2.55.4 25.175 255.7 21.062 34.6 0.88277 23.375 502.77 o.8501y 2-jj. 8 18.078 60.5 20.064 442.51 Benzene values not given, but as authors used capillary ot Guye and Baud who calibrated the bore from the benzene results of Ranisay and Shields, 2 . 1 0 1 2 is assumed as correct. * Average of 2 . i108 and 2 . Io12 used for finding r for the comparison.
WEIGHT OF A FALLING DROP AND THE LAWS OF TATE. VII.
IO55
Table XXIV (Contiwed). Ramsay and Shields; kB = 2.1012.
zoo 80 90
264.3 260.8 259.9
500.7 367.2 314.4
IWO I IO
I20
Guye and Baud;
519.6 413.0 373.0
.... .... ....
.... ....
2.
I 108.
t.
509 470 437
....
.... .... ....
262.8 258.2 260.5
Renard and Guye; kB =
12.9' 31.3 46.9
259. I 258.3 257.9
kg = 2.1012.
t
9.5O 55.6 77.0
321.7 299.0 277 ,o
7
55.0' 65.9 73.5
260.0 260.0 259.9
($)$.
418.0 394.0 381 .o
tC
259.0 258.6 260.0
Sicrface Tensions. t.
rR&S.
IO0
24.81* 23.60 22.39 21.18 19.97 17.55 16.32
20
30 40 50 70 80
rG&B.
rR 8: G.
rY&S.
24.50 23.27 22.04 2 0 . 89
24.00 22.82 21.64 20.44 19.29 16.99" I5.84*
24.64 23.36 22.08
20.80
19.52 17.35 16.32*
19. 7 1
17. 39 16. 47*
TABLE XXV. a''
a'
Liquid
Pyridine. . . . . . . . . . . . . . . . . . . Methyl isobutyrate. . . . . . . . . . Ethyl propionate. . . . . . . . . . . . Methyl propionate. . . . . . . . . . Methyl acetate. . . . . . . . . . . . . . Propyl acetate . . . . . . . . . . . . . Methyl butyrate. . . . . . . . . . . . Ethyl acetate.. . . . . . . . . . . . . .
a'.
0,003534 0.004295 0.0042 I I 0.004426 0.005143 0.004233 0.004 100 0.004665
1
--
fc=constant
---,
a'a"
a".
0.002624 0.00332 I 0.003231 0 . -3443 0.003979 0.003244 0.003 I48 0.003630
Ethyl formate.. . . . . . . . . . . . . 0.004847 0.003681 Amyl formate. . . . . . . . . . . . . . 0.003884 0.003070 Propyl formate.. . . . . . . . . . . . 0.004171 0.003060 Methyl formate.. . . . . . . . . . . . o.wg165 0.003888 The values for benzene are af = 0.004203 and a" taking t, = 288.5', the constant is found to be 0.5243.
tc
.
348.0 279.9 286.7 270.7 233.7 285.5 294.5 256.8
tc
from kg.
346.9 282.6 286.8 265.5 233.5 288.3 294.0 255.6
250.6 225.1-228.7 305.7 318.6-316.2 297 .o 260.6-267. I 234.4 201.8-206. I = 0.003201, from which,
IOjh
Gi:iXEK,\I,,
l'HYSIC~\I, .\KD XNOIIGANIC.
Discussion of the Results. 'Taking up the liquids in the order they are given in the tables, we find for methyl isobutyrate (SIV) that the calculated ,\-slue of t, is constant froin drop n-eiglit, but has a slight trend downwarcl according to the results from capillary risc, though it must be conceded that the numbers l)y the latter method arc hardly consistent, for Rcnard and Ciiye find LL sudden break between jjO and 7 j ' of I , 3 O, although from 3 0 . j' to 3 j O there is only utle of o 2 '. In other words, it would seem that there is some cri-or in the cq)illar>-rise, as judged froni the /(, valiic, which occurs bctwccn j 5 O and 75 O for Renard and Guye, and between 4 6 . 2 ' and 7 8 . 2 O for Ramsay and Aston. This may be x-ery well due to the use of density \ d u e s which are not quite consistent a t the high and the low temperatures. Comparison of the surface tension values as calculated by the two methods, where those from drop weight are free from any effect oi density, s h o w an excellent agreement with the results of Ramsay and Aston, and one that is truly remarkable, eyen t o the extrapolated .values, with those of Renard and Guye. 113th ethyl propionate the agreement in the values of fc, which is constant by both methods, is excellent, while the drop weight surface tensions are found to lie between the values found by Ramsay and Aston in two capillaries of differing bore. The tc values for methyl propionate by drop weight may be considered as constant, the variation, which is not excessive, being due probably to the density. If a trend is assumed here i t is certainly in the opposit direction from that found from the capillary rise. The tL \-alues in one of Ramsay and Xston's tubes is also practically constant, but is slightly smaller throughout than the drop weight value, while the other s h o k a higher value eve11 than that, at ioo, and then remains constant a t a value midway I,etwceii that of the other and the drop weight. The coinparison of the surface tcnsion yalues from the two methods shows an agreement which is excellent. With ethyl formate the fL salues show an increase with the tempera-. ture throughout, the \.allies from the two methods being practically identical when with the same density values the tc's are calculated from the surface tension values of drop weight. Tliese latter, except that extrapolated through 4 4 . j O, lie between the surface tensions from the two tubes of Ranisay and Xston. We shall return to the trend in the t, \ d u e s again. Xethyl acetate is the only liquid among those investigated, which leads to a t, value in agreement with the observed critical temperature, and is found both by drop weight and capillary rise, for the mean of all the Ramsay and .Iston values is 2 3 4 O , as compared with 2 3 3 . jo by drop weight, and 2 3 3 . 7 ' observed directly. The surface tensions here also
WEIGHT O F A FALLING DROP AND THE LAWS OF TATE. VII.
IO57
agree in an extremely satisfactory manner, including one of the extrapolated values, although the other, extrapolated through 44. I ', does not. It is to be remembered here that the drop weight surface tension is one that a t 78.3O with the constant 2 . I 2 I 2 would still give 233.5 ', while the capillary rise value would lead to a higher result. In the case of propyl acetate, the slight variation in the t, values is probably due to the density used, and is not thought to indicate a trend. The means of all the Ramsay and Aston values is 288.9', while that from the drop weight is 288.3 '. The surface tensions from drop weight are very slightly smaller throughout than those from capillary rise, but the difference is less than that often noticed between the values from the two tubes of Ramsay and Aston, which should be identical in result. In the case of methyl butyrate the drop weight tc is identical a t all three temperatures, while a slight variation is shown by the capillary rise method, the results of which differ, when found from the different tubes, by I '. Considering all this as due to variable error in the capillary rise values, we find the mean 1, to be 294.7', as compared to the constant 294' from drop weight. The surface tensions here, except for IO', where the capillary rise values differ considerably among themselves, is very good indeed. Propyl formate shows an increase in t, with the temperature by both drop weight and capillary rise, the values from drop weight not agreeing very well, either with respect to t, or to surface tension, with those from capillary rise. The behavior of this liquid was found to be striking, in that when heated for a few hours a t 60°, a reversible reaction appears to take place which increases the drop weight, when i t is determined again Thus heating for 2 hours, then allowing the liquid to cool natura t IO'. ally, and determining the drop weight a t IO', a value 27.434 is obtained, as against 27.337 for the unheated sample. After standing for 16 hours, this weight is reduced to 27.430, and after IO days to 27.366. Heating to Go' and cooling suddenly, as in a distillation, leads to a value of 27.337, i. e . , one identical with that of an unheated sample. Since nothing else in the behavior of the liquid indicated a reason for this, i t is assumed that a definit reaction takes place on raising the temperature, which reverses slowly, unless the cooling is very rapid, when it returns a t once to its original state. Using the value a t 10' found after heating, the drop weight fc would be increased to 262.2, which is in better agreement with one of the Ramsay and Aston values. As far as can be found from the paper, Ramsay and Aston always worked a t the higher temperatures first, gradually lowering the temperature by reducing the pressure over the boiling liquid which heated the bath. This would account for their higher values a t the low temperature-for the actual state a t the higher temperature would then persist a t the lower one. With the drop weight,
rojP
&XAL
P H I ClCAL . l h D IIiORGANIC.
on tile other kind the 7vei~Iitat the lower temperature was always determined iron: n sain;jlc_ diich, if it had been heated. had returned to its oriqina! state XIethyl formate is a li~,iiid v hicli liad been in\ estigated by Ramsay and Shield\, arid n n s coti\equentlv n n t studied by Ramsay and Aston. Hew aqair; a x alue of tb increasing with the temperature is observed by both methods The drop weight surface tensions here a t the low temperature: d o not agree well with those from the capillary rise, but Ihe aqreeincr,t he(-omei I ~ t t e and r better as tlie temperature of obsen ation increases. a en thoiiqh all but one of the drop weight values are extrapolated. until the agreement is perfect. This would indicate a behavior similar to that of propyl formate, the low values of the capillary rise being inftienced by tlie persistence of the high temperature conditions, n-liile the drop XreiAht is unaffected by it When the possibility of this effect disappears. the two methods lead to idelltical results. Here the lower ~ a l u e sby drop xcight, being smaller than they should be, while that a t 2 j 8 O is less affected, n-ould produce a curve which when combined would naturally eliminate a t the higher temperatures the effect of the heat reaction noticeable a t the low temperatures. Amyl formate has bcen ins estigated only by Homfray and Guye. The sample u5ed here w . 3 probably not piire, and certainly the densities employed were not satisfactory, as the three ~ a l u e sgixen by Honifray and Guye did not allon an accurate el trapolation & l i s will be observed, the t p values from capillary rise are \-e"; constant, while those from drop iveight dccrease slightly, and are smaller throughout This may, of coui\e be due either to the effect of density or to an impurity. The surface tensions differ a\ do the ~ a l u e sof fc this w d d 5eeiii to indicate (ha1 ~ ! I L punty d the liquid used for the drop weight is questionable It rail bc coricliided there that through no fault of tlic drop weight method, the results from capillary rise are probably the niore correct. For e t l i ~ lacetate a constant fc is found both from drop weight and from capillary riqe a5 found by G u y and Baud and Kenard and Guye, although the ~alut.., differ considerably. Ramsay and Shields find a downward trend. 'l'he difference in the three values of surface tension from capillan rise is best shown perhaps when all are calculated to the same temperature. It \Trill be obser,ed here that it is a t tlie low temperatures especially that the results of the 3 obsersers of capillary rise differ, difierences of I per cent. and more being common. It is unfortunate that this liquid ~\-a\not inxestigated by Ramsay and Xston in tiieil- two tubes. Xs it is, there is no apparent reason why drop weight and capillary rise shoiild diii^rr as thcy do, especially in Iiew of the other excellent agrcenicnts One thing is certain from the constant t,, both irom drop weig!it ant! Iioiii capillary rise, izz., ethyl acetate is to be regarded as normal in molecular weight, $. e., i t is non-associated.
WEIGHT OP A FALLING DROP A N D THE LAWS OF TATE. VII.
1059
It. will be seen from the above that according to the new definition of normal molecular weight the following liquids are to be regarded as normal and non-associated : methyl isobutyrate, ethyl propionate, methyl propionate, methyl acetate, Fropyl acetate, methyl butyrate, amyl formate (from capilZary rise values of t,), and ethyl acetate. Ethyl formate, methyl formate, and propyl formate do not satisfy this definition and consequently are not to be considered as normal; but their behavior may in all cases be due to such a reversible reaction as is indicated above in the case of propyl formate when heated. A sample of amyl formgte was heated to 230’ in the presence of mercury in a closed tube for 4 hours, ,i. e., submitted to somewhat the same conditions that would hold during an observation of the critical temperature. On opening the tube considerable pressure was observed, while the liquid, which had a somewhat different odor, showed a drop weight a t IO’ of 27.309, as compared to the value 27.464, obtained before heating. This, of course, is not to be considered as the opposit behavior to that of propyl formate when heated t o 60°, for here an actual decomposition takes place. If this decomposition always takes place in the determination of the critical temperature, it would account for the differences between the 304’ observed and the fictitious critical temperature, t,, found above, w”., 32 I ’. Table XXV gives the results of t, calculated by aid of the Walden rea’ a‘/ lationship t, = constant - , where the values of a’ and a” are found a’”’
+
from the equations w,
= W,(I--LV’~)
and
=
”t=zo(l-a”t).
It
dl
will be observed here that the agreement is as good as can be expected (remembering the multiplication of error in finding a’ and a”), i. e., in all cases where the 1, found from k , is constant.
Conclusions. The results of this investigation may be summarized as follows: I . It is shown by aid of the new definition of normal molecular weight in the liquid state, i. e., the finding of a calculated value of t, from the equation w
(3 -
=
k , (t, -t -6), which does not v a ~ ywith the
temperature of observation, using in all cases the value of k, found for benzene and taking t, = 288.5 ’, that methyl acetate, ethyl acetate, propyl acetate, methyl butyrate, methyl isobutyrate, methyl propionate, ethyl propionate, and amyl formate are normal in molecular weight, i. e., are non-associated. 2. It is found that only in the case of methyl acetate does the calculated t, agree with the observed critical temperature, the fictitious critical temperatures, t,, being the higher in all the others except ethyl, methyl
1060
GENER.\L,
PHYSICAL .\ND IKORGANIC.
and propyl formates, where i t approaches the obsemed value with increased temperature. 3. Methyl, ethyl and propyl formates show varying values of 2, with the temperature I n one of these (it is probably true for all) i t is shown that apparently a reaction which is reversible is caused by increased temperature, which can be res ersed by sudden cooling, but which persists on dou- cooling, leading a t the lower temperatures to a higher drop weight (and also t,) than the unheated sample It is only after some days that this heated sample again returns to its original, unheated value. This reaction is probably what causes the drop to be heavier than it should be a t the higher temperature, and to lead to the value of t, which is larger a t 60' than a t o o by 6' in the maximum. We cannot say then that these three formates are either associated or normal: but ?imply that increased temperature causes a reaction of an unknown nature to take place. 4 Surface tensions in dynes per centimeter, calculated from the drop weight by multiplication by the ratio of the benzene constant for capillary rise to that for drop weight, are found to agree exceedingly well with those of Ramsay and Aston. The agreement of methyl formate with the figures of Ramsay and Shields is not so good, nor that of amyl formate with those of Homfray and Guye (although this is probably due to the impurity of the sample used with drop weight), while the values for ethyl acetate vary considerably from those of the workers on capillary rise, although these do not agree well among themselves 5 . The values of t, calculated from the modified Walden relationship agree as well with those from the 12, formula as can be expected, except for ethyl, methyl and propyl formates, where since the k , values are variable, no agreement can be expected LAIKJRATORY OF
P H Y S I C A L CBRMISTR'I
-
[COXTRIRUTIONSFROM
THE
H ~ V E M E Y E R L~BORATORIES OF COLVMBIi UNIVERSITY,
No 194 1
THE WEIGHT O F A FALLING DROP AND THE LAWS O F TATE. VIII. THE RELATIONSHIP EXISTING BETWEEN THE WEIGHT O F THE DROP, THE DIAMETER O F THE TIP FROM WHICH IT FALLS, AND THE SURFACE TENSION O F THE LIQUID. 13Y J
LIVINGSTON R
M O R G A A A h D JFSqS'h Y
Received May 6.
CANS
ig11
I t has been shown in previous papers that tor a)zy one tzp the Laws 0 ) Tate, z i z . the xezght of a jnllang dro9 I T proportqonal to the surface tension of the liquid; and thP w e & !o) the di o p dect eclses wtth increased temfieralurc, are true. The object of this paper is to present the results of a study
